Waste materials from many industries comprise organic materials, often organic greases and oils. In some instances these waste oils include highly toxic chemicals (contaminants) therein. A well-known example is the waste material from conventional wood treatment facilities.
At a typical wood treatment facility, wood is preserved by being soaked or dipped in a vat of oil that has a preservative therein. For example, a facility for the treatment of telephone poles, railroad ties, or the like, may use large vats that contain an oil having pentachlorophenol (PCP) dissolved therein. A typical treatment vat used for such processes contains an organic solution containing about five percent PCP.
Waste organics, often containing a substantial amount of PCP, have often been dumped into a pit area located near the treatment facility. While this is particularly disturbing with respect to current pollution control standards, it must be understood that such treatment facilities have operated for many decades with substantially little change in the overall soaking and/or treatment procedure. Thus, many sites exist which came into existence well before the more recently imposed pollution controls.
The pollution problem is exacerbated by the nature of the industry. Very often a treatment facility was established, short term, near a location where a substantial amount of wood was milled, or treated wood was needed. After sufficient operation to accommodate the "local" need, the facility was closed and sometimes moved to a different location. Thus a plurality of abandoned dump sites exist throughout the country.
Over time, the contaminated organic materials may be transported, by groundwater, out of the immediate dump area, contaminating a widespread area. Since the organics often include a substantial amount of highly toxic materials therein, this migration poses a substantial health and environmental hazard.
It is noted that while the problem of pollution from organics in soils has been described with respect to a specific industry involving wood treatment, the problem exists with respect to a variety of industries that have similarly generated organic wastes dumped into pits or the like. The wood treatment industry merely provides a well-known and notorious example, and one which often involves particularly hazardous PCP.
No satisfactory method of overall soil treatment and/or purification has been previously available. Generally treatment methods have involved either incineration alone, microbial treatment, or some combination thereof. These have not been completely satisfactory, in part for the reasons discussed below.
A frequently used conventional method of purification is incineration. For a typical incineration process, a large incinerator is assembled near a contaminated site. Soil material is excavated from the site, in bulk, and is incinerated. The incineration process generally destroys much of the organic material, but it also results in a large volume of ash material, much of which is fused into hard cakes or blocks. This material, which may still be substantially contaminated, is typically then stored in a secure dump, leaving the excavated site open. After a particular site has been cleaned, the incinerator is typically disassembled and moved to a new location.
Incineration, on its own, has been a generally undesirable process. First it is energy inefficient, that is a large amount of energy is consumed in operating the incinerator at sufficient temperatures and for a sufficient length of time to lead to effective purification of the large volume of materials involved. Secondly, product gases and materials from the incineration may be a problem. Further, the large amount of contaminated ash formed creates a disposal problem.
A second method of purifying contaminated soil is through the use of microbial action. Generally, especially for the oil/PCP problem, microbial purifications have proved undesirable. While in the laboratory microbial action may be shown to capably detoxify material, in the field it is less efficacious. First, temperature, moisture and oxygen control may be essential, and difficult to achieve. Also, a wide variety of chemical concentrations may be found throughout a single dump site, and from site to site. Concentration variations generate unpredictability. Further, complete microbial detoxification of concentrated contaminants may take a fairly long period of time, and during that period of time further leaching from the dump site may occur. Finally, soil variations and dump site environment variations pose substantial hurdles to the effective, predictable, action of microbes.
What has been needed has been an effective method of purifying soil that has been contaminated with organic material or the like. Generally, to be effective the method must not only accomplish the desired result, i.e. substantially clean soil, but it also should be relatively cost effective. That is, what has been needed has been a cost effective method to replace, provide an alternative to, or at least operate effectively in conjunction with, conventional soil treatment processes.